SECC Winter Climate Outlook
Date updated: December 5, 2008
Season starts with a cold Fall. Fall came early to Southeast this year, with an October cold snap bringing freezing temperatures as far south as Tallahassee, FL. Many records were set over the Southeast on the morning of October 29th, with Tallahassee and Jacksonville registering the lowest temperatures on record in the month of October. The cold weather continued in November with yet another record-setting cold snap on November 18 and 19 with freezing temperatures extending south of Gainesville, FL. Over the last 30 days, the Southeast is averaging temperatures 4 to 6 degrees F below normal and could end up ranking among the top 10 coldest falls on record.
30-day temperature departures from normal. (courtesy SERCC)
Rainfall over the Southeast has generally been below average, with the exception of the Big Bend region of Florida, southern Alabama, and the southern half of Georgia, which received a widespread 2-4 inches or more from a strong low pressure system on November 29-30. Otherwise, dryness continued in the drought-plagued regions of north Georgia, north Alabama, and North Carolina. The peninsula of Florida has also been quite dry over the past 2 or more months, but that is not unusual now that Florida’s dry season has set in.
Rainfall departures from normal (inches) for the month of November from radar estimates. (courtesy NOAA NWS)
For more detailed information on recent weather, please see the resources below:
- Florida Automated Weather Network
- Georgia Automated Environmental Monitoring Network
- Alabama Office of the State Climatologist
- Southeast Regional Climate Center
- NWS Radar-derived Precipitation Totals
The latest U.S. Drought Monitor shows exceptional drought, which has persisted for over two years now, hanging on over a small area of north Georgia and the Carolina’s. Other areas of north Alabama, north Georgia, and the Carolina’s continue in drought ranging form moderate to severe. For more information on the ongoing drought and a statement from the State Climatologist on Georgia’s drought, see the links below.
Neutral Pacific means more variable weather patterns over the Southeast. With Neutral conditions firmly in place in the tropical Pacific Ocean, there is no indication that temperatures or rainfall will be either above normal or below normal. More variable weather is common in neutral winters, with periods of very cold weather mixed in with warm spells. With the very cold we have experienced thus far this fall, chances are good that the winter season will see a continuation of this cold weather. Chill hour accumulations are ahead of schedule so far this year, while growing degree-days are lagging behind normal.
Severe freezes that can impact citrus and other winter crops are more likely this year. Studies have shown that of the dozen or so catastrophic freezes that have impacted the Florida citrus industry since the late 1800’s, nearly all of them have occurred during times of Neutral conditions in the Pacific. We believe that the predominant jet stream patterns set up by El Niña and La Niña tend to “block” the major intrusions of Arctic air masses that cause these severe freezes. With neither in place this season, the jet streams are more susceptible to the dramatic dips, or “troughs” that can allow these air masses further south. For more information, see our winter freeze forecast:
Near-normal rainfall is the best forecast, as there is no El Niño or La Niña to tip the balance towards wetter or drier than normal. Keep in mind that winter is the critical recharge period for surface and groundwater in Alabama, Georgia, and the Carolina’s. The good coverage and slow soaking nature of winter rainfall that is cause by fronts and low pressure systems is much more effective at refilling rivers, lakes, reservoirs, and aquifers than the scattered summer thundershowers. In addition, the colder temperatures and mostly dormant vegetation result in much less loss to evapotranspiration. Normal or above normal rainfall during the coming season is critical to easing the prolonged drought conditions these states have experienced.
For more detailed information on climate impacts in the Southeast, see the Climate Risk tool
Neutral conditions prevail in the Pacific Ocean
This winter should be free from the effects of El Niño/La Niña. Sea surface temperatures along the equator in the eastern and central Pacific Ocean have been close to normal since April of 2008. Near normal sea surface temperatures in this area of the Pacific is known as Neutral conditions. Historically, neutral conditions occur roughly half the time. At other times, this area of the Pacific can swing into periods where it is much warmer than normal, known as El Niño, or much colder than normal, referred to as La Niña. The Pacific Ocean was in a fairly strong La Niña last winter and spring.
Neutral conditions are expected to continue through the winter of 2008/2009 and possibly longer. However, the atmosphere over the Pacific is giving mixed signals. The Southern Oscillation Index, which is a difference in surface barometric pressure between the central and western Pacific, is strongly positive at this time and more consistent with La Niña. Additionally, the easterly trade winds over the central Pacific have been consistently stronger than normal which could lead to a cooling of Ocean temperatures. On the other hand, weather patterns over the Southeast U.S. have been colder than normal with frequent cold front passage which is very uncharacteristic of La Niña conditions. This all means there may be a chance that we slip back into La Niña sometime this winter, but that is not a high likelihood. There is almost no chance of El Niño developing.